With the improvement of people's living standards, display equipments such as mobile phones, cameras, computers and televisions are widely applied by people. TFTs, as important elements of the equipments, directly affect the display effect of the display equipments. A TFT generally comprises an active layer, a gate insulating layer, a gate electrode, a source electrode and a drain electrode and is generally applied in, e.g., a liquid crystal display (LCD), an organic light-emitting diode (OLED) device and an e-paper display device and taken as a switching element or a drive element.